Self-adjusting printed circuit board support and method of use

ABSTRACT

A printed circuit board support including a first member having a planar upper surface for supporting a printed circuit board. At least one second member is movably coupled to a first side of the first member and movable toward and away from the side of the movable member, and a bias source biases the second member in a direction away from the first member.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a self-adjusting printed circuit boardsupport for use at a printed circuit board screen printing station. Moreparticularly, the present invention relates to a self-adjusting printedcircuit board support for use at a screen printer station in a printedcircuit board assembly line.

2. Description of Related Art

A common step used during the assembly of active and passive devicesonto a printed circuit board is a screen printer station. Typically atthis station the circuit is already on the printed circuit board andsolder is squeegeed through a screen or template onto the circuit inpreparation for subsequent stations where active and passive componentsare placed on the board. In addition, a screen printer may be used aswell to place the circuit pattern on the printed circuit board. Priorart tooling or supports used for holding the printed circuit board inthe screen printer station are generally designed for the narrowestprinted circuit board, thus leaving large areas of larger printedcircuit boards unsupported. Other known support devices require the useof multiple fixed supports which are each designed for a specific widthof the various sized printed circuit boards to be assembled.

SUMMARY OF THE INVENTION

A universal printed circuit board support which can fully supportvarious sizes of printed circuit board in a screen printer and in thefabrication and/or assembly environments is desirable, and is providedby the present invention.

In one aspect on the invention a printed circuit board support comprisesa first member having a planar upper surface for supporting a printedcircuit board. At least one second member is movably coupled to a firstside of the first member and movable toward and away from the side ofthe movable member; and a bias source biases the second member in adirection away from the first member.

In another aspect, the present invention provides a printed circuitboard support for use at a printed circuit board assembly station whichis width-wise adjustable to support printed circuit boards of variouswidth-wise dimensions.

The support comprises a pair of parallel outer rails, each of which hasouter surfaces for abutting engagement with one of a pair of spacedsurfaces on a positioning device at the assembly station. A pair ofparallel inner rails are provided between and spaced from the pair ofouter rails, and a mid-block is provided between and spaced from thepair of inner rails. The mid-block and inner and outer rails have uppersurfaces for supporting the printed circuit board at the assemblystation. A first plurality of rods, each of which is fixed at one endthereof to the first one of the outer rails, extend through a firstrespective plurality of transverse holes in a first one of the innerrails. A second plurality of rods, each fixed at one end thereof to asecond one of the outer rails, extend through a second respectiveplurality of transverse holes in a second one of the inner rails. Aplurality of components for biasing each one of the outer rails and theinner rails outwardly from the mid-block are associated with the rods.The outer rails are moveable toward each other against the bias of theplurality of biasing components by compressive forces applied againstthe outer rails to fit the outer rails in abutting engagement with thespaced surfaces on the positioning device.

The self adjusting printed circuit board support of the presentinvention provides maximum support for a wide variety of sizes ofprinted circuit boards used, for example, in the production of memorymodules. When used in a typical screen printer the self-adjustingprinted circuit board support of the present invention supports in itslength-wise direction the entire length of a printed circuit board. Whencompressed width-wise, it self adjusts to support the entire width ofthe printed circuit board.

The support of the present invention is readily compressed by hand toallow placement into or onto a positioning device between a spacedefined by surfaces of the positioning device and the support expandsupon its release to fill the space. When the support is left in theassembly station during a change over to a different width circuitboard, the support will automatically adjust to the width fixed by anywidth-wise adjustment in the space between the surfaces of thepositioning device.

The above and other features and advantages of the invention will bemore readily understood from the following detailed description which isprovided in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a self-adjusting printed circuit boardsupport for use at a printed circuit board assembly station inaccordance with the present invention;

FIG. 2 is an exploded view of the support of FIG. 1;

FIG. 3 is a top plan view of the support of FIG. 1;

FIG. 4 is a side elevational view of the support of FIG. 3;

FIG. 5 is a cross-sectional view taken along line V—V of FIG. 3;

FIG. 6 is a perspective view of the support of FIG. 1 in a fullycompressed state and with a printed circuit board thereon;

FIG. 7 is a perspective view of a screen printer with its cover removed;

FIG. 8 is a cross-sectional view taken along line VIII—VIII of FIG. 7;and

FIG. 9 is a top plan view of the screen printer showing a self-adjustingprinted circuit board support installed therein and supporting a printedcircuit board.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1-4, there is shown an embodiment of aself-adjusting printed circuit board support 10 in accordance with thepresent invention. The support 10 has a pair of parallel outer rails12,14 each of which has an outwardly extending lip 13,15 for abuttingengagement with a plurality of spaced surfaces 90-95 (FIG. 8) on apositioning device 97 (FIGS. 7 & 8) at an assembly station. A pair ofparallel inner rails 24,26 are located between and spaced from the pairof outer rails 12,14. The support 10 also includes a mid-block 16 whichis located between and spaced from the pair of inner rails 24,26. Themid-block 16 has an upper surface 17 for supporting a printed circuitboard at the assembly station. Likewise, the inner 24, 26 and outer 12,14 rails have an upper surface, co-planar with the upper surface ofmid-block 16, for supporting the printed circuit board.

A pair of rods 18, each fixed at one end thereof 19 to a first one 12 ofthe outer rails 12,14, extend through a first plurality of transverseholes 22,23 in a first one 24 of the inner rails 24,26. A second pair ofrods 25, each fixed at one end 27 thereof to a second one 14 of theouter rails 12,14, extend through a second pair of transverse holes29,32 in a second one 26 of the inner rails 24,26. The first and secondpair of rods 18,25 extend through respective holes 30,31 in themid-block 16. Each hole 30,31 in the mid-block 16 has therein a linearball bearing assembly 28 (FIG. 5) for supporting a respective one of therods 18,25.

Each one of the transverse holes 22,23;29,32 in the two inner rails24,26 has a counter-sunk portion 33,37 on each side for seating a coilcompression spring 34,34′;35,35′ therein. Each one of the rods 18,25 hasa circumferential recess 53 at each end thereof. The recess 53 receivesan E-clip 54 (FIG. 5) therein after the rods 18,25 are passed throughrespective springs 34,34′;35,35′, respective inner rails 24,26,respective springs 34,34′;35,35′ and the inner-block 16. Each E-clip 54abuts an underside of a respective linear ball bearing assembly 28 (FIG.5) to prevent the its respective rod from passing through the linearball bearing assembly 28 under the bias of the springs 34,34′;35,35′.However as shown in FIG. 3, the E-clips 54 have an outer dimension whichis smaller than holes 60,61;62,63 in the inner rails 24,26 and holes64,65;66,67 in the outer rails to permit the rods 18,25 to pass throughthe inner rails 24,26 and into the outer rails 12,14 when the support 10is in a compressed state as shown in FIG. 6.

The coiled compression springs 34,35 function to bias each one of theouter rails 12,14 and inner rails 24,26 outwardly from the mid-block 16.The outer rails 12,14 are moveable toward each other against the bias ofthe coiled compression springs 34,34′;35,35′ to position the support 10between spaced surfaces on the positioning device 97 of a screenprinter, and upon release the support expands to provide contact betweenthe outer surfaces 13,15 on the outer rails 12,14 with the spacedsurfaces on the positioning device 97.

The printed circuit board support of the present invention isparticularly suitable for use at a screen printer assembly station.

The printed circuit board support functions such that the outer rails12,14 are moveable between a fully open position as shown in FIGS. 1 and3 when no compressive forces are applied thereto, and a fully compressedposition when force is applied to compress the support as shown in FIG.6 wherein the outer rails 12,14 are in contact with the inner rails24,26 and the inner rails are in contact with the mid-block 16.

When no compressive forces are applied to the outer rails 12,14, therods 18 extending from the outer rail 12 and the rods 25 extending fromthe other outer rail 14 extend through respective inner rails 24,26 andinto linear ball-bearing assemblies 28 in the transverse holes 30,31through the mid-block 16 as shown in FIG. 3. When the printed circuitboard support is fully compressed as shown in FIG. 6, the rods 18extending from the first outer rail 12 pass through the transverse holes30,31 of the mid-block 16, the holes 60,61 in the inner rail 26 and intoholes 64,65 of the second outer rail 14. In like manner, the rods 25connected to the second outer rail pass through a second set oftransverse holes 30,31 in the mid-block 16, through holes 62,63 in thefirst inner rail 24 and into a pair of holes 66,67 in the first outerrail 12.

The mid-block 16 is elongated and has a plurality of perforations 21which extend through the mid-block 16 from the upper support surface 17.When in position in the screen printer 70 as shown in FIG. 7, thesupport 10 is positioned over a conduit 76 which is in communicationwith a vacuum source 74. The pull of the vacuum generated by the source74 through the port 76 and the perforations 21 act to draw the printedcircuit board against the upper support surface 17, and thus hold theprinted circuit board in position during the screen printer operation.

The outer rails 12,14 each have a pair of support handles 36,38; 40,42secured respectively thereto by rivets or screws 44. The support handles36,38; 40,42 are manually engageable for applying compressive forces tothe printed circuit board support 10 during installation in thepositioning device 97 of the screen printer station.

A portion of a screen printer station 70 is shown in FIGS. 7 and 8 witha cover (not shown) removed. The positioning device 97 includes opposingstep-like spaced surfaces 90,92,94;91,93,95 formed from sheet metal.Each one of the shaped surfaces has a leg 92,93 connected to andextending upwardly from a steel plate 96, and an upwardly extendingportion 90,91 spaced outwardly by horizontal portion 94,95. Internalconveyor belts 72,73 are spaced above horizontal portions 94,95,respectively.

As shown in FIG. 8, the lips 13,15 of the outer rails 12,14 are inabutting engagement with the step-like spaced surfaces 92;93 when thesupport 10 is released.

With reference to FIGS. 7 and 8, the support 10 is positioned on thesteel plate 96 and is held thereon by magnets 50 (FIG. 2) which arepositioned in recesses 52 (FIG. 3) located in the underside of themid-block 16.

Printed circuit boards 80,81,82 are sequentially supplied to thescreenprinter 70 by a pair of feeder conveyor belts 85,86. Each printedcircuit board is transferred from the conveyor belts 85,86 to theinternal conveyor belts 72,73 of the screenprinter 70. The conveyingsystem is indexed such that each printed circuit board stops in theposition shown in FIG. 7. The positioning device 97 including the steelplate 96 and the sheet metal opposing step-like spaced surfaces90,92,94;91,93,95 are raised to lift the support 10 upwardly between theinternal conveyor belts 72,73 to contact the underside of the printedcircuit board 81. The printed circuit board 81 is drawn to the support10 by the vacuum applied through port 76, to the underside of thesupport 10, and through the perforations 21 in the mid-block 16. Thevacuum acts to retain the printed circuit board 81 against the uppersupport surface 17 of the mid-block 16, and the upper surfaces of theinner 24, 26 and outer 12, 14 rails, with the printed circuit boardoverhanging the sides of the support 10 by a very slight distance. Theprinted circuit board 81 is lifted off the internal conveyor belts 72,73at which position the screenprinting step is carried out. Afterscreenprinting, the support 10 is lowered by the screenprinterpositioning device 97 to return the printed circuit board 81 to theinternal conveyor belts 72,73. The internal conveyor belts 72,73 in turnpasses the printed circuit board 81 to exit conveyor belts 87,88 thatare external to the screenprinter 70 while another printed circuit boardis fed by the feeder conveyor belts 85,86 to the screenprinter 70.

In an alternative embodiment, a pair of snugger bars 78,79 (FIG. 9)engage the side surfaces of the printed circuit board 81 while in thescreenprinter 70 and after the board 81 and support 10 are lifted by thepositioning device 97. In this embodiment, both the vacuum 74 and thesnugger bars 78,79 the printed circuit board in a fixed position duringthe screenprinting operation. After the printing operation, the snuggerbars 78,79 are retracted, and the support is lowered by the positioningdevice 97 to place the printer circuit board 81 back on the internalconveyor belts 72, 73 for passage to the external conveyor belts 87,88.

Thus, the present invention provides a universal printed circuit boardsupport which can fully support various sizes of printed circuit boardsin a screenprinter and/or in other fabrication and assemblyenvironments.

Although the present invention has been described with preferredembodiments, it is to be understood that modifications and variationsmay be utilized without departing from the spirit and scope of thisinvention, as those skilled in the art will readily understand. Suchmodifications and variations are considered to be part of the invention,provided they come within the scope of the appended claims and theirequivalents.

What is claimed is:
 1. A printed circuit board support comprising: apair of parallel outer rails, each having outer surfaces for abuttingengagement with a plurality of spaced surfaces on a positioning deviceat said assembly station, said outer rails having respective uppersurfaces for supporting a printed circuit board; a pair of parallelinner rails between and spaced from said pair of outer rails, said innerrails having respective upper surfaces for supporting a printed circuitboard; a mid-block between and spaced from said pair of inner rails,said mid-block having an upper surface for supporting a printed circuitboard at said assembly station; first plurality of rods each fixed atone end thereof to a first one of said outer rails and extending througha first plurality of transverse holes in a first one of said innerrails; a second plurality of rods each fixed at one end thereof to asecond one of said outer rails and extending through a second pluralityof transverse holes in a second one of said inner rails; and a pluralityof components for biasing each one of said outer rails and said innerrails outwardly from said mid-block, said outer rails being movabletoward each other against the bias of said plurality of biasingcomponents by compression forces applied against said outer rails. 2.The printed circuit board support of claim 1 wherein said positioningdevice is at a screenprinter station.
 3. The printed circuit boardsupport of claim 2 wherein said outer rails are movable between a fullyopen position when no compressive forces are applied thereto and a fullycompressed position when sufficient force to compress said support isapplied.
 4. The printed circuit board support of claim 2 and whereinsaid first and said second plurality of rods extend at least into saidmid-block when no compressive forces are applied to said outer rails. 5.The printed circuit board support of claim 2 wherein said first and saidsecond plurality of rods extend through the respective opposing innerrail and at least into the opposing outer rail when said outer rails arefully compressed.
 6. The printed circuit board support of claim 5further comprising a bearing in each one of said first and secondplurality of transverse holes, said first and said second plurality ofrods extending through a respective one of the bearings when nocompressive forces are applied to said outer rails.
 7. The printedcircuit board support of claim 2 further comprising a support handleattached to each end of each one of said outer rails wherein the supporthandles are engageable for applying compressive forces to the printedcircuit board support.
 8. The printed circuit board support of claim 2wherein said mid-block is elongated, and wherein at least oneperforation extends through said mid-block from said upper supportsurface, said at least one perforation communicating with a vacuumsource for drawing a printed circuit board against said upper supportsurface.
 9. The printed circuit board support of claim 2 wherein aplurality of perforations extend through said mid-block from said uppersupport surface to communicate with a vacuum source for drawing aprinted circuit board against said upper support surface.
 10. Theprinted circuit board support of claim 2 wherein said first and saidsecond plurality of rods extend through the respective opposing innerrails and into the respective opposing outer rail when said outer railsare fully compressed.
 11. The printed circuit board support of claim 2wherein said biasing components bias said outer rails and said innerrails outwardly from said mid-block in directions as defined by the axesof said first plurality of rods and said second plurality of rods. 12.The printed circuit board support of claim 2 wherein said mid-blockcomprises a plurality of recesses in the underside thereof, and whereina plurality of magnets are seated in said recesses.
 13. The printedcircuit board support of claim 2 wherein said outer surfaces are anoutwardly extending lip formed on each one of said outer rails.
 14. Theprinted circuit board support of claim 2 wherein said biasing componentsare coiled compression springs.
 15. A self-adjusting printed circuitboard support for use at a screenprinter station in a printed circuitboard assembly line, said support comprising: a pair of parallel outerrails, each having outer surfaces for abutting engagement with aplurality of spaced surfaces on a positioning device at said assemblystation said outer rails having respective upper surfaces for supportinga printed circuit board; a pair of parallel inner rails between andspaced from said pair of outer rails, said inner rails having respectiveupper surfaces for supporting a printed circuit board; a mid-blockbetween and spaced from said pair of inner rails, said mid-block havingan upper surface for supporting a printed circuit board at said assemblystation; plurality of perforations extending through said mid-block fromsaid upper support surface to communicate with a vacuum source fordrawing said printed circuit board against said upper support surface; afirst plurality of rods each fixed at one end thereof to a first one ofsaid outer rails and extending through a first plurality of transverseholes in a first one of said inner rails; a second plurality of rodseach fixed at one end thereof to a second one of said outer rails andextending through a second plurality of transverse holes in a second oneof said inner rails; and a plurality of components for biasing each oneof said outer rails and said inner rails outwardly from said mid-block,said outer rails being movable toward each other against the bias ofsaid plurality of biasing components by compression forces appliedagainst said outer rails; said outer rails being movable between a fullyopen position when no compressive forces are applied thereto and a fullycompressed position when sufficient force to compress said support isapplied thereto, said first and said second plurality of rods extendingat least into said mid-block when no compressive forces are applied tosaid outer rails, and said first and said second plurality of rodsextending through the respective opposing inner rail and at least intothe opposing outer rail when said outer rails are fully compressed. 16.A printed circuit board support comprising: a first member having aplanar upper surface for supporting a printed circuit board; at leastone second member, having a contact surface for contacting a positioningsurface of a printed circuit board assembly station, movably coupled toa first side of said first member and movable toward and away from saidfirst side of said first member, said at least one second member havingan upper surface for supporting a printed circuit board; at least onethird member movably coupled to a second side of said first member andmovable toward and. away from said second side of said first member,said at least one third member having upper surface for supporting aprinted circuit board; a bias source for biasing said second member in adirection away from said first member; and a plurality of perforationsextending through said planar upper surface of said first member tocommunicate with a vacuum source for drawing a printed circuit boardagainst said upper surface.
 17. A printed circuit board supportcomprising: a first member having a planar upper surface for supportinga printed circuit board, said first member comprising a plurality ofrecesses in the underside thereof, and wherein a plurality of magnetsage seated in said recesses; at least one second member, having acontact surface for contacting a positioning surface of a printedCircuit board assembly station, movably coupled to a first side of saidfirst member and movable toward and away from said fist side of saidfirst member, said at least one second member having an upper surfacefor supporting a printed circuit board; at least one third membermovably coupled to a second side of said first member and movable towardand away from said second side of said first member, said at least onethird member having an upper surface for supporting a printed circuitboard; and a bias source for biasing said second member in a directionaway from said first member.